I have 3 kids now (1, 5 and 7). I the older two are showing more interest in music now, and I'm not sure where to start with them. It sounds like for my 7 year old WH&P is out. My daughter turned 5 two months ago, is she out on that too? Can ETC get them to AP? I just want to try to give them the best foundation (including both RP and AP) if I can.

When it comes to learning absolute pitch, yes, the 5-year-old is probably out. All the available science points to the critical window of learning being between ages 2 and 5. It wouldn't be a waste of time to try WHaP, because it would provide a solid early approach to musical education, and the youngest child could gain some observational exposure to the material, but a 5-year-old's brain will not learn quite the same way, nor achieve the same result, as a younger-than-5.

ETC was not really designed for children. Despite the colorful, cartoony look of the program, its repetitive gameplay and comparable lack of reward (no intermissions, no "you did great" messages, etc) may not be compelling enough to keep children interested.